Hi Tammy, that looks very much like a good old native house spider (Tegenaria domestica), very common and harmless as far as I know! But I just read there are 5 species, some larger than others but all native to the UK. Hope this helps!

Thanks Mellojo I had a look at the website, but I'm not sure still. I know the giant house spiders and have captured and released many over the years. This is different from any I've ever seen - a much chunkier spider than any previous. Also the abdomen is much bigger.

I very much think that Mellojo is correct & this is a Tegenaria/house spider. There is no reson to believe it is anything but a native spider. This is a female, they have larger (chunkier) abdomens than males. The fangs do not look unusually large for this kind of spider. They are not generally implicated in bites, certainly not with venomous bites that carry notable side effects, though they can puncture human skin. She is harmless to us and if you let her go, she will probably return to her web.